This post is part of PowerMock series examples. The code shown in examples below is available in GitHub java-samples/junit repository.

In Mock static methods in JUnit with PowerMock example post, I have given information about PowerMock and how to mock a static method. In the current post, I will demonstrate how to verify given static method was called during execution of a unit test.

Example class for unit test

We are going to unit test a class called LocatorService that internally uses a static method from utility class Utils. Method randomDistance(int distance) in Utils is returning random variable, hence it has no predictable behavior and the only way to test it is by mocking it:

public class LocatorService {

    public Point generatePointWithinDistance(Point point, int distance) {
        return new Point(point.getX() + Utils.randomDistance(distance), 
            point.getY() + Utils.randomDistance(distance));
    }
}

And Utils class is:

import java.util.Random;

public final class Utils {

    private static final Random RAND = new Random();

    private Utils() {
        // Utilities class
    }

    public static int randomDistance(int distance) {
        return RAND.nextInt(distance + distance) - distance;
    }
}

Nota bene: it is good code design practice to make utility classes final and with a private constructor.

Verify static method call

This is the full code. Additional details are shown below it.

package com.automationrhapsody.junit;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.internal.verification.VerificationModeFactory;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class LocatorServiceTest {

    private LocatorService locatorServiceUnderTest;

    @Before
    public void setUp() {
        PowerMockito.mockStatic(Utils.class);

        locatorServiceUnderTest = new LocatorService();
    }

    @Test
    public void testStaticMethodCall() {
        locatorServiceUnderTest
            .generatePointWithinDistance(new Point(11, 11), 1);
        locatorServiceUnderTest
            .generatePointWithinDistance(new Point(11, 11), 234);

        PowerMockito.verifyStatic(VerificationModeFactory.times(2));
        Utils.randomDistance(1);

        PowerMockito.verifyStatic(VerificationModeFactory.times(2));
        Utils.randomDistance(234);

        PowerMockito.verifyNoMoreInteractions(Utils.class);
    }
}

Explanation

Class containing static method should be prepared for mocking with PowerMockito.mockStatic(Utils.class) code. Then call to static method is done inside locatorServiceUnderTest .generatePointWithinDistance() method. In this test, it is intentionally called 2 times with different distance (1 and 234) in order to show the verification which consists of two parts. First part is PowerMockito.verifyStatic(VerificationModeFactory.times(2)) which tells PowerMock to verify static method was called 2 times. The second part is Utils.randomDistance(1) which tells exactly which static method should be verified. Instead of 1 in the brackets you can use anyInt() or anyObject(). 1 is used to make verification explicit. As you can see there is second verification that randomDistance() method was called with 234 as well: PowerMockito.verifyStatic(VerificationModeFactory.times(2)); Utils.randomDistance(234);.

Conclusion

PowerMock provides additional power to Mockito mocking library which is described in Mock JUnit tests with Mockito example post. In the current post, I have shown how to verify static method was called. It is very specific as verification actually consists of two steps.

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Related Posts

• PowerMock examples and why better not to use them
• Mock static methods in JUnit with PowerMock example
• Mock JUnit tests with Mockito example